/Engine/Source/Runtime/Core/Public/Misc/CoreDelegates.h
Called when the OS needs control of the music (parameter is true) or when the OS returns control of the music to the application (parameter is false). This can happen due to a phone call or timer or other OS-level event. This is currently triggered only on iOS devices.
static [TMulticastDelegate](API\Runtime\Core\Delegates\TMulticastDelegate)< void(bool)> UserMusicInterruptDelegate;